Ms. Ernst, a resident of St. Louis, is most concerned about the welfare of lab rodents. Animal advocates say rats and mice make up 90% of animal testing conducted in university laboratories and other research facilities in the U.S. In 2002, the Animal Welfare Act was amended to exclude rodents from protections offered to bigger lab animals including dogs, monkeys and even guinea pigs.

"Rats and mice tend to get a bad rap" that influences people from the time they are children, says Ms. Ernst. "We just have these biases built in that are not really representative of who they are."

Animal-rights advocates in the U.S. have scored coups in recent years for an assortment of uncuddly animals. A new law requires bigger cages for egg-laying chickens in California. Foie gras, a delicacy made from the livers of fattened geese and ducks, has been banished from some restaurant menus.

But public sympathy for rats and mice hasn't grown much in three decades since the animal-rights movement first organized in the U.S. Viewed as pests and greeted with shrieks, rats are much less likely to attract public sympathy than, say, the furry bunnies that serve as the poster critters for cutting back on animal testing.